(1) Field of the Invention
The invention relates to a thermocouple device and, more particularly, to a thermocouple device having a ceramic bead insulator.
(2) Description of the Prior Art
A thermocouple is a temperature sensing device. In integrated circuit manufacturing, thermocouples are used, for example, to measure the temperature in an oxidation furnace. For example, an oxidation furnace may be used for growing of oxide, drive-in of dopants, low pressure chemical vapor deposition, annealing, and so on. All of these processes must be performed at specific temperatures. A thermocouple is used to check the accuracy of the temperature setting of the furnace.
FIG. 1A illustrates a typical thermocouple having a ceramic bead-type insulator. A pair of parallel wires are connected at one end to a thermocouple 10 and at the opposite end to a connector plug 12. The ceramic beads shield the wires and prevent the wires from shorting and twisting. This type of thermocouple may be used in any type of high temperature environment in which flexibility is desired; that is, the wires can bend.
In the thermocouple design of the prior art, shorting of the thermocouple wires may occur. For example, as shown in FIG. 1B, because of the ceramic bead 14 design, the thermocouple wires between the beads are easily exposed. The exposed wire 16 is easily shorted when heated. Because of thermal expansion of the wires, the wires may be twisted or deformed 18. Twisted or deformed wires also are shorted easily when heated. Shorting of the wires results in incorrect temperature sensing causing loss of control of the oxidation furnace temperature, and the potential of scrapped wafer lots.
It is desired to improve the design of the ceramic bead insulated thermocouple so that the potential for shorting is greatly reduced.
U.S. Pat. No. 5,043,023 to Bentley shows a metal-sheathed thermocouple having a ceramic insulator between the wires and the sheath. U.S. Pat. No. 5,811,761 to Kita et al and U.S. Pat. No. 6,102,565 to Kita et al disclose thermocouples having ceramic sheaths molded around the wires wherein the ceramic sheaths are encased in a protective pipe. U.S. Pat. No. 4,937,434 to Nakao shows movable thermocouples in a furnace. U.S. Pat. No. 4,950,870 to Mitsuhashi et al shows a heater and a thermocouple thermometer.
Accordingly, a principal object of the present invention is to provide an improved thermocouple having a ceramic bead insulator.
In accordance with the objects of this invention an improved thermocouple having a ceramic bead insulator is achieved. A pair of wires in parallel is joined at a first end to a thermocouple and joined at a second end to a connector. The pair of wires is threaded through each of a series of interlocking ceramic beads wherein the series of interlocking ceramic beads forms the ceramic bead insulator.